In gas turbine engine oil systems, an oil shut-off valve (OSOV) is typically used to terminate a flow of oil through the oil system. This may be desirable, for example, at engine shutdown in order to avoid flooding the bearings supporting the rotating elements of the gas turbine engine. An oil shut-off valve may also be used to enable the parts downstream of the valve to be certified as fire resistant instead of fire proof.
Some OSOVs are actuated by pressurized air, which can be bled off from the high pressure (HP) compressor of the gas turbine engine. The HP spool (i.e. the HP compressor and the HP turbine) drives the pumps used to scavenge oil and to supply oil to the bearings. At a certain pressure, the pressurized air opens and closes the OSOV. The air system must be sealed from the oil system. When this seal malfunctions it may provide a path for the oil to contaminate the air system and vice-versa.